1. Field of the Invention
This invention relates to a device with which a constant shearing effect can be obtained during the continuous shearing of the pile of lengths of material of varying thickness.
2. Description of the Prior Art
To achieve a smooth surface or a more or less pronounced pile, material such as velvet, plush and the like, is shorn with machines consisting basically of a rotary cutter arrangement operating in conjunction with a fixed bottom blade and a table on which the material is fed forward. To set the depth of shear, that is to say the actual gap between top cutter, bottom blade and table, use is generally made of gauges introduced between the table and the bottom cutter or between the material and the bottom cutter.
The machine operator judges the degree of density by the effort required to move these gauges and raises or lowers the cutter until he considers it is in the right position. To enable goods in the form of runs to be shorn economically, a number of such runs are sewn together and fed continuously through the machine. However, when several runs of material of one and the same quality are to be shorn, it is seldom found that the individual pieces are of uniform thickness.
Even with goods of the same kind, thickness variation mostly arises in the gauging equipment, as a result of variations in batch washing or of fulling.
Should the operator fail to regulate the gap between the table and cutter, the pile will vary in depth. A conscientious worker will adjust the depth of shear by gauge for every run, which naturally wastes a lot of time.
Moreover, uniform treatment of the various pieces of material depends on the skill of the operator, who can always make errors of judgment. Devices have already been proposed, by means of which the thickness of the first piece of material can be ascertained between the bottom blade and a sensing device associated with an indicator gauge fitted to the table. Then, with the aid of the same gauge, the bottom blade is adjusted in the same conditions until the gauge reading for the next piece of material again corresponds to the measurement indicated for the first piece.
This adjustment has to be made manually and the drive of the shearing machine must be stopped or disconnected during adjustment and re-setting, so that the output of the entire installation is reduced accordingly.
U.S. Pat. Ser. No. 3,683,468 discloses a shearing apparatus with two cutters which are movable towards and away from one another. A device is disclosed for measuring the value of the shear gap during relative motion of the shearing members.
When a voltage source is switched on, the voltage is applied directly across the cutters and the measuring device indicates the current flow set up. Since the electrical resistance between the cutters is directly dependent upon the value of the air gap between the two shearing members, an exact measurement of the cutter gap can be provided by the measuring device. With this device a measurement of the width of the shearing member gap is possible, on the basis of which further devices for the adjustment of the shears or of the shear table can be brought into action when the apparatus is in operation. A similar apparatus is also disclosed in French Pat. Spec. No. 1,422,111, but neither discloses any means which simultaneously take into account and control operation of the apparatus in dependence upon both the thickness of the material and the gap between the shearing members at any given instant.
An object of the present invention is to eliminate, at least partially, the drawbacks and disadvantages of existing adjustment devices. During normal shearing, that is to say without interruption of work, the thickness of the runs of material to be shorn can first be measured and then, in the event of a sudden variation in thickness, the gap between the shearing bar or table and the shearing blade can be appropriately reset automatically to defined limits, without the need for any manual intervention in the setting or re-setting of the depth of shear. Such automatic adjustment or correction of the depth of shear can be carried out, if need be, during the shearing of any particular piece of material. Mostly, however, sudden variations in thickness occur before and after the join between two pieces of unequal thickness that have been sewn together. Since, owing to the substantial thickening of the material at the seam, the gap between the cutter and the shearing bar must be enlarged in any case, to allow passage of the seam, the invention provides for the setting or re-setting of the original depth of shear, according to the thickness variation before and after the seam, to be determined and carried out during the said period, while the seam is passing through. Enlargement of the gap as the seam passes through can be achieved by conventional means by the sudden raising of the cutter arrangement as a whole from the shearing bar or by suddenly lowering or swinging the shearing bar away from the cutter arrangement. Once the seam has been passed, the shearing gap automatically re-set in accordance with the invention comes into play, with its corresponding new depth of shear.